This invention relates generally to electronic musical instruments, and more particularly to electronic organs and the like, wherein a multi-frequency generator is used to generate a plurality of frequencies corresponding to the plurality of frequencies associated with one octave of a musical keyboard. Musical frequencies of other octaves, either higher in frequency or lower in frequency, are generated by multiplication or division of the base frequency obtained from the multi-frequency generator.
Electronic organs have become relatively common in the musical industry and provide means for simulating the sounds produced from larger wind operated pipe organs and the like. Such electronic organs differ from one another substantially in certain specific respects, such as whether the tone produced from the organ is obtained by a tone generator associated with additive or subtractive circuits. They also differ as to the specific type of generator used to obtain the base frequencies, as for example, whether they are transistor or tube oscillators, wind-driven reed elements, rotating tone wheels, and the like. However, all of these electronic organs can be distinguished by certain common features. In particular, each organ has a plurality of tone generators, there being one tone generator for each note of the keyboards associated with a two-manual organ. Furthermore, associated with the less expensive types of electronic organs there is a single tone generator associated with the pedal tones, these tones being derived by one or more divider circuits which divide the frequency from the keyboard. However, only one pedal note at a time can be played with this type of circuit so therefore, only one tone generator is needed.
It will be immediately apparent that there is a rather significant redundancy of tone generators used in prior art types of electronic organs. However, since the maximum number of notes that normally can be played at any one time is twelve, one note for each finger of the two hands and one note for each foot when manipulating the foot pedals, there are a multitude of tone generators that are not in use. In popular organ playing, it is unusual to use more than one pedal tone at a time and it is to be expected that no more than perhaps five notes will be played at any one time by the fingers of both hands. Some effort has been made to reduce the redundancy of tone generators needed by using turnable oscillators, wherein an oscillator is shared with two or three adjacent notes on the keyboard. This is done under the presumption that only one of these notes will be played at any one time. The presumption does not always hold true however, and this is at best a low cost approach to developing electronic musical instruments of this type. However, there are still more tone generators needed than can be utilized at any one time.
In any event, the oscillator or other tone generators provide an audio frequency oscillation which bears a direct relation to the frequency of the note being played. In the case of subtractive type organ circuits, the note generated is the fundamental of the note played. In this case a large number of harmonics are provided by the generator, and the undesired harmonics are filtered out in accordance with the organ stop then being used. On the other hand, in the case of additive organ circuits, the tone generated may be a sub-harmonic of the tone played and this sub-harmonic is then multiplied to achieve the desired frequency.
All of the electronic organ circuits heretofor utilized have been of the type which require discrete active and passive components formed in large chassis or secured to large circuit boards, such as printed circuit boards and the like. These discrete components may take the form of individual tubes or transistors as well as including inductance and capacitance elements which provide the necessary LC circuits for the oscillators. This type of prior art configuration and any of the above types of organ arrangements is relatively expensive to manufacture, and furthermore, requires a substantial amount of maintenance over the life of the organ. As well as corrective and preventative maintenance, occasional tuning of the oscillator circuit is required to maintain the organ tone qualities in tune.